One important factor in the distance a two-way radio will communicate is its power output. This power output is measured in watts. Youve likely heard an FM radio station say they are broadcasting at 50,000 or 100,000 watts. Well, a handheld business-type two-way radio usually broadcasts at 1-5 watts. A vehicle mobile radio may broadcast anywhere from 5 to 100 watts. The more watts a radio has, the farther it can transmit.
Why is this? When water moves through a pipe it loses pressure along the way. When electricity flows along a wire it loses current. When an object is rolling, it will eventually stop rolling due to friction. Radio waves operate by the same laws of physics as everything else so there will be signal loss along the way. But if you apply more water pressure, more electrical current, or get the rolling object moving faster, you'll get more distance out of all of them. The same is true for a radio signal. Increasing the power in watts at the source helps overcome any "resistance" along the way.
Certain models of two-way radios provide a feature of selecting the power output of the device. The different modes offered to the user are high power, medium power and low power modes. Most radios include only the high and low power mode. This feature is also known as the Power Selectable feature.
When a 2-way radio is used in for short range communication, it's always best to use the low power mode. Always try to use the lowest power setting. Running the device in low power mode conserves battery power therefore giving more time between charges.
Another reason to use the lower power setting is that your radios won't transmit as far, therefore limiting the number of people outside your group that can hear your conversations.
The high-power mode should be reserved for long-range communication, or for when there are lots of obstacles to penetrate.